Which of the following cells is NOT a part of cellular barriers?
(a) Interferons
(b) Natural killer cell
(c) Kupffer cell
(d) Polymorphonuclear lymphocytes

Options

A. Interferons
B. Natural killer cell
C. kupffer cell
D. Polymorphonuclear lymphocytes

Answer

To determine which of the following cells is NOT a part of cellular barriers, we need to analyze each option provided:

1. **Interferons (Option A)**:
- Interferons are proteins produced by virus-infected cells to signal neighboring cells to enhance their defenses against viral infection. They play a role in the immune response but are not cells themselves. Therefore, they do not constitute a cellular barrier.

2. **Natural Killer Cells (Option B)**:
- Natural killer (NK) cells are a type of lymphocyte that play a crucial role in the innate immune response. They are responsible for identifying and destroying virus-infected cells and tumor cells. Since they are actual cells that contribute to the cellular barrier, this option is not correct.

3. **Kupffer Cells (Option C)**:
- Kupffer cells are specialized macrophages located in the liver. They help in filtering and removing pathogens and dead cells from the blood, thus providing a protective barrier in the liver. As they are cells that participate in immune defense, this option is also not correct.

4. **Polymorphonuclear Lymphocytes (Option D)**:
- Polymorphonuclear lymphocytes (PMNLs), also known as neutrophils, are a type of white blood cell that is essential for the innate immune response. They are among the first responders to sites of infection, thus acting as a cellular barrier against pathogens. Therefore, this option is not correct either.

After analyzing all the options, we conclude that the only option that does not represent a cell involved in cellular barriers is:

**Correct Answer: (a) Interferons**